Astronomy Specialist


$1,179.00 AUD
SKU: BA2458200

Baader Planetarium

Flatfield Barlow

  • M42 x 0.75 Male
  • M42 x 0.75 Female
  • 2" barrel

0.24 kg


Important! Make sure you read the warranty information at the bottom of the page before purchasing the FFC.


The Baader CaF2 Fluorite Flatfield Converter can be combined with every optical system for photography and visual observations as best and most sophisticated Barlow lens in the world. The FFC is an apochromatic, multi-coated fluorite lens system with 10 x higher line resolution than the best projection eyepieces available. It has a massive 90mm image circle for use with medium format cameras.

For almost 20 years, Baader's customers had asked again and again: "Do you have a barlow lens or projection eyepiece – but with a flat field – which can be used with medium format (6x7 Pentax) cameras for imaging sun, moon and planets, but without the typical loss of sharpness?"

In 1997, one of the designers of the Zeiss APQ lenses calculated the ultimate projection system with a flat image field. To actually make this design become reality, extreme types of glasses were needed. In this case, two multicoated fluorite-lenses - at that time and until today - a nightmare to produce.

The result was an optical system with an unmatched sharpness, with a ten times higher resolution of line pairs than a Zeiss Abbe eyepiece. Even so the days of emulsion film cameras are long gone, this lens system has persisted to be "the sharpest barlow ever made".



By changing the distance to the camera sensor, you can vary the magnification between 3x and 8x. The optimum line resolution is set at 4x magnification, where you have the full sharpness over an image circle of 90 mm diameter. On-axis, the sharpness is only limited by your telescope – even at a magnification factor of 15x.

The FFC can be connected onto every T-2 thread and its 2" main body likewise fits into every 2" eyepiece clamp. With the help of our many adapters, you can connect it just about any telescope.

For best results, you need to keep a certain distance to the original focus point. Please take a look at the PDFs in the Download section of the Baader website for technical information.



The Baader-FFC contains lenses which are made of real calcium-fluorite crystal. CaF2 has got an impressive refractivity which enables construction of the ultimate lens system that can deliver an incredible amount of sharpness across a very broad spectral range. Unfortunately, such sophisticated optics are very sensitive to tension caused by temperature differences.

Under no circumstances must CaF2 be exposed to sudden or high changes in temperature. Do not use it for photographing the sun – the fast and high changes in temperature could destroy the Fluorite lenses. Defects caused by thermal stress can be detected and measured here in house and are explicitly excluded from the warranty.

Also avoid fast changes in temperature during night-observation/imaging. Never use any Fluorite-lenses (especially not in the front lens of a telescope) at -20°C and then all of a sudden put it it into your living room at +20°C or more! In such a case, the resulting severe temperature stress just as well can be detected, when the lenses end up damaged.

Every CaF2 optic needs time to adapt to the surrounding temperature. To do so, for example bring the optical system into the outside in an insulated box and allow it to cool down inside that box over the time of an hour. Keep the box closed but outside. After the imaging session put the FFC back into the same box and allow it to gradually warm up inside that box while bringing it inside the house. Keep it there for at least one hour until you open the box and check that any moisture can dry out.


Magnification factor
3 - 8 x
Optical design
Barlow, field flattener
Connection telescope side
2" barrel, T2 (M42 x 0.75) female thread
Connection eyepiece side
T2 (M42 x 0.75) thread
Weight 240 g
SKU BA2458200

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$1,179.00 AUD

Optical design

Flatfield Barlow

Image circle

90 mm

Focal ratio


Focal length

Optical thickness


M42 x 0.75 Male, M42 x 0.75 Female, 2" barrel


Colour or Mono

Pixel size

Sensor dimensions


Sensor diagonal

Quantum efficiency

Read noise

Fullwell capacity

Bit depth


Camera backfocus

Filter size

Filter size

Bandpass (FWHM)

Bandpass (FWHM)

Glass thickness

Mount type

Payload capacity

Latitude range

Dovetail saddle

Slew speed


Periodic error correction

Counterweight shaft

Azimuth adjustment range

Internal diameter

Illuminated diameter

Compatible telescope external diameter


0.24 kg




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